It is well known that optical arrangements typically require alignment along a common centerline (or optical axis) in order to function properly. For example, in order for a lens to function properly in conjunction with an image detector, typically an optical bore sleeve is used to hold the lens in alignment with the common centerline (or optical axis) of the bore sleeve and the image detector. Of course, the lens must be appropriately centered within bore sleeve, so that the lens, the bore sleeve and the image detector are all in alignment with the common centerline (or optical axis.)
In a discussion of lens mounts at pages 490-492 of Modern Optical Engineering published by McGraw Hill Inc., (1990), which are hereby incorporated by reference, author Warren J. Smith points out that optical lens elements are almost always mounted in a close-fitting sleeve. Various ways of centering the lens within the bore sleeve that are known in the prior art are discussed by Smith, including: retaining the lens by a wire spring ring in a V-grove extending into the inner bore of the sleeve as shown in FIG. 1A; retaining the lens by a flat spring ring as shown in FIG. 1B; retaining the lens by three grooved rods arrange with respect to each other at one hundred and twenty degree angles as shown in FIG. 1C; retaining the lens by threaded lock rings as shown in FIGS. 1D and 1E; retaining the lens by a thin, so called "spinning" shoulder of the sleeve, which is folded over in a burnishing step as shown in FIG. 1F; and retaining the lens by cementing it in place, with a trough for cement overflow, as shown in FIG. 1G.
While such examples of the prior art each provide some advantages, other challenges still remain. For example, if the lens and bore sleeve are made to loose tolerances to provide for ease of manufacturing and low cost, then typically the bore sleeve is made oversized to allow for variations in the lens and variations in the bore sleeve. Accordingly, the lens fits loosely in the oversized bore, resulting in poor optical alignment and performance.
Alternatively, if the lens and bore sleeve are made to tight tolerances then the lens fits closely in the bore, providing good optical alignment and performance. However, manufacturing the lens and bore sleeve to such tight tolerances is much more difficult and expensive than manufacturing to loose tolerances.
As another alternative, ease and low cost are achieved by manufacturing the lens and bore sleeve to loose tolerances, while good optical alignment and performance are achieved by subsequent careful and complex realignment procedures that center the lens within the bore sleeve. However, such careful and complex realignment procedures are made much more difficult and expensive to perform, in light of the loose tolerances of the lens and bore sleeve.
What is needed is a simple, easy and convenient method and apparatus for centering the lens within the optical bore sleeve, while maintaining good optical alignment and performance, even when the lens and bore sleeves are made to loose tolerances for ease of manufacturing and low cost.